For example, a fuel injection system includes a fuel injection valve provided to a direct injection gasoline engine for jetting fuel directly into a combustion chamber of the engine. In general, a direct injection engine has a structure, in which stratified combustion is formed to improve fuel consumption. A direct injection engine may perform wall guide combustion, in which spray is introduced along a piston wall so that a mixture gas is led to an ignition plug. Alternatively, a direct injection engine may perform spray guide combustion, in which spray is jetted and directly ignited without being introduced by a wall.
In recent years, further improvement in fuel consumption and reduction in harmful components in exhaust gas are demanded.
U.S. Pat. No. 6,543,408, U.S. Pat. No. 6,575,132, and U.S. Pat. No. 6,748,917 (JP-A-2002-539365) disclose an example of the spray guide combustion, in which fuel splay is not introduced along a piston wall, so that influence may not be exerted to airflow. In this structure, the region of stratified combustion can be enlarged, and adherence of a fuel to a piston can be reduced.
U.S. Pat. No. 6,561,436 (JP-A-2002-525486) discloses a structure for jetting fuel spray in the form of a hollow conical shape. In this structure, a valve body accommodates a valve member, which is lifted outwardly from a valve seat of the valve body, thereby forming a flow passage therebetween. Fuel is jetted throughout the circumferential periphery of the flow passage to form a spray in the form of a hollow conical shape. The valve member extends through the valve body, so that the seat is relatively large in diameter. Accordingly, an actuator such as a piezoelectric element or a super magnetostrictive element is applied for producing a large driving force in order to operate the valve member.
However, in the structure of US '436, a fuel pipe needs to be additionally provided for introducing surplus fuel therethrough into a fuel tank for control of hydraulic pressure in a hydraulic pressure control chamber. For example, JP-A-4-12165 discloses a structure for driving a valve member using an actuator producing relatively small force. In this structure, the actuator adjusts flow of fuel to control hydraulic pressure in a hydraulic pressure control chamber, so that a valve member is lifted and seated corresponding to the hydraulic pressure. In this operation, surplus fuel is produced for controlling hydraulic pressure in the hydraulic pressure control chamber. This surplus fuel is returned to a fuel tank through a fuel passage. In this structure, a fuel piping system of the fuel injection apparatus becomes complicated due to the additional fuel passage. Consequently, manufacturing cost of the fuel injection system may be increased.